Real Driving Emissions – are you ready?

Emissions Analytics was recently asked to write an article for Automotive World’s Megatrends magazine. This month’s newsletter is a summary of that article which considers the potential impact of the proposed changes to the New European Drive Cycle.

Emissions Analytics’ data resource, from tests on more than 800 vehicles, is transforming the economics of obtaining emissions data for OEMs who are tasked with understanding and acting upon the proposed legislative changes concerning Real Driving Emissions (RDE) and the move towards the World Harmonised Light Test Cycle and Procedures (WLTC/P).

The new testing system, developed by global representatives for the United Nations Economic Commission for Europe is due to be finalised in the spring of 2015. This test cycle is more representative of real-world driving and the test procedures should be more robust than those associated with the New European Drive Cycle (NEDC).

One of the reasons for the proposed change is the growing gap between the number of miles per gallon certified during the NEDC test and the fuel economy achievable by real drivers on the road which can be seen clearly below.

Using Emissions Analytics’ real-world data, the blue line on the graph below illustrates how this gap is growing, at about two percentage points per year, and is likely to continue to expand if left unchecked. With the introduction of the WLTC/P in 2017, we predict the gap will close by between half and two-thirds (shown below in green), depending on how stringent the final protocol is.

Although this will bring the European divergence closer it will not equal the USA variance, where the more stringent five-cycle system is in operation.

Nov 14 chart

Bold line: EA data 
Dashed line (historical): Other sources of data
Dashed line (future): Model based prediction by EA

The European Parliament and European Commission have proposed this new test be introduced in 2017, although there are challenges and opposition from some parts of the automotive industry that would like longer to adapt to the changes.

One of the challenges facing OEMs is the profile of the NEDC replacement, the WLTC. The International Council on Clean Transportation has estimated that the effect on the EU CO2 target value will be an increase of around 5-8%. Emissions Analytics believes the increase could be higher than this.  If nothing were changed in the targets, OEMs would need to deliver further efficiencies in their vehicles, and consumers in some countries could find themselves paying more vehicle tax.

There is a methodology under development for translating the existing NEDC results into WLTC, but this is still work-in-progress and has limitations. What is clear is that forewarning of how current vehicles perform on the test can bring significant benefits to the engineers developing the vehicles which will be on the road when the WLTC/P is adopted. This is why some manufacturers use Emissions Analytics’ data to ensure compliance and to stay competitive, benchmarking their own progress against that of their closest rivals.

In times when manufacturers are under increasing pressure to be open and honest about their vehicles’ true in-use performance, plus with the imminent legislative changes which will formalise this requirement, there has never been a greater need for a reliable and robust source of data which can offer the insight and intelligence needed.

Emissions Analytics will shortly be making their data available to the automotive sector directly via a new, subscription based software platform called RDEanalytics. More will follow on this in a later newsletter but for a sneak preview or to find out more email us now.

Hybrid efficiency put to the test

Despite common perception, the advantage of hybrids over frugal diesels is often illusory, if judged solely on fuel economy. Having tested over 30 hybrids in the UK and US, Emissions Analytics is able to analyse the data to understand how they really perform.

To illustrate the point we have taken a sample of 10 vehicles tested since 2013 – two standard hybrids versus 8 diesels – from the real-world fuel economy testing we conduct with What Car? in the UK. Each has an engines in the 1.5 to 2.2 litre range, power up to 150bhp, two-wheel drive and with hatchback, saloon or estate body style. The table shows the sample, ranked by fuel economy with the best MPG at the top:

Make Model Engine Size Derivative Fuel Transmission True MPG
Honda Civic 1.6 i-DTEC ES Diesel Manual 67.2
Skoda Octavia 1.6 Greenline III TDi CR Diesel Manual 61.9
Peugeot 308 1.6 Allure BlueHDi Diesel Manual 60.8
Mazda 3 2.2 SE-L Nav Skyactiv-D Diesel Manual 59.4
Toyota Auris 1.8 Touring Sports Icon VVT-I Petrol hybrid Automatic 58.7
Citroen C4 Cactus 1.6 Flair e-HDI Diesel Automatic 57.8
Toyota Yaris 1.5 Excel VVT-I Petrol hybrid Automatic 57.8
Peugeot 2008 1.5 Feline e-HDi Diesel Manual 57.7
Volkswagen Golf 1.6 Bluemotion TDi Diesel Manual 56.8
Honda CR-V 1.6 i-DTEC SR Diesel Manual 56.5

While hybrids deliver good fuel economy in real driving, they can be eclipsed by up to 10mpg by some non-hybrid diesels. And that is after having taken into account any net changes in battery charge levels, to ensure that the hybrids are not penalised over our cycle. For certain driving patterns however, hybrids may still be the better option. Over our complete dataset of more than 500 vehicles in the UK, we can quantify how average MPG changes under congestion and aggressive and fast driving.

Urban congestion penalty Urban aggression penalty Extra urban benefit
Diesel -6.0% -8.4% 18.4%
Diesel hybrid -2.5% -12.9% 1.1%
Petrol -8.3% -6.5% 27.4%
Petrol hybrid -3.3% -7.5% 8.5%

What this data shows is that hybrids suffer much less than their ICE equivalents under congested urban driving: on average a 3% penalty compared to 7%. In contrast, by doubling the average rate of acceleration the MPG falls by more for hybrids, especially diesel hybrids.

Comparing motorway driving to town driving, all types of vehicle show better MPG on the former, but the difference between hybrids and ICE vehicles is dramatic – typically because the downsized engines found in the hybrids are less suited for high speed motorway cruising.

Even more than their tolerance of congestion, the value of hybrids may be in their pollutant emissions, as even the cleanest diesels typically exceed the regulated values of NOx. In a recent report by the International Council on Clean Transportation, which analysed data from Emissions Analytics, the average exceedance was seven times for the latest Euro 6 diesel cars.

This compares to petrols, which generally meet the regulated NOx standards, even in real-world driving. Carbon monoxide is higher for the petrols, but again within the regulated values. Therefore, petrol hybrids have the benefit over ICE diesels in their effect on air quality, made even better as a proportion of urban driving will be on battery, with zero emissions. Although not included here, plug-in hybrids can show this pattern even more strongly.

In summary, hybrids deliver good but not best-in-class fuel economy, but they are typically the cleanest, and if you are a light-footed, congested town driver, they are ideal.